Stethoscope Cleaning Practices Fail to Eliminate Bacterial Contamination

A new study reveals that intensive care unit (ICU) stethoscopes are loaded with bacteria, including Staphylococcus aureus, and that common cleaning methods are ineffective.

Researchers at the University of Pennsylvania (Penn; Philadelphia, USA) and the Children's Hospital of Philadelphia (CHOP; PA, USA) conducted a study designed to examine bacterial contamination of stethoscopes in use in an ICU, including 20 traditional reusable stethoscopes, 20 single-patient-use disposable stethoscopes, and 10 unused single-use disposable stethoscopes as a control. Two additional sets of practitioner stethoscopes were sampled before and after cleaning using standardized or practitioner-preferred methods. The researcher used 16S rRNA gene deep sequencing to profile the bacterial populations.

The results showed all 40 of the ICU stethoscopes were significantly contaminated with a rich and diverse community of bacteria, including those related to common healthcare-associated infections (HAIs). Staphylococci were found in abundance on all stethoscopes, with more than half of them having confirmed contamination with S. aureus. Other bacteria, such as Pseudomonas and Acinetobacter, were also widely present on the stethoscopes, albeit in smaller quantities. Cleaning impact was assessed by cleaning for 60 seconds with a hydrogen peroxide (H2O2) wipe or by practitioner usual methods, which included alcohol swabs, H2O2 wipes, or bleach wipes for different durations.

The results revealed that all cleaning methods reduced the amount of bacteria, but failed to consistently bring contamination to the level of clean, new stethoscopes. The standardized cleaning method reduced bacteria on half of the stethoscopes to the clean level, while only 10% reached that level when cleaned by the practitioner-preferred method, which suggests stethoscopes are significant potential vehicles for infection transmission. In the other stethoscopes, bacterial community composition did not significantly change. The study was published on December 12, 2018, in Infection Control & Hospital Epidemiology.

“While molecular sequencing allowed researchers to identify all the types of bacteria and the quantity of bacteria, the DNA test could not distinguish live from dead bacteria, so it is not clear if the stethoscopes are responsible for the spread of disease-causing agents,” said senior author Professor Ronald Collman, MD, of the Penn Perelman School of Medicine. “This study underscores the importance of adhering to rigorous infection control procedures, including fully adhering to CDC-recommended decontamination procedures between patients, or using single-patient-use stethoscopes kept in each patient's room.”

Related Links:
University of Pennsylvania
Children's Hospital of Philadelphia